Reaction motor operable by liquid propellants and method of operating it



Nov. 2, 1954 F. J. MALINA ETAL REACTION MOTOR OPERABLE BY LIQUIDPROPELLANTS AND METHOD OF OPERATING IT Original Filed May 8, 1943 INERTGAS JOHN PARSONS FRANK J MAL/NA INVENTOR.

w MW ATTOR E Y Z,693,?7 Patented Nov. 2, 1954 REACTION MOTOR OPERABLE BYLIQUID PRO- PELLANTS AND METHOD OF OPERATING IT Frank J. Malina and JohnW. Parsons, Pasadena, Calif., assignors, by mesne assignments, toAerojet-General Corporation, Azusa, Calif, a corporation of OhioOriginal application May 8, 1943, Serial No. 486,236, now

Patent No. 2,573,471, dated October 30, 1951. Divided and thisapplication September 1, 1950, Serial No. 182,742

2 Claims. (Cl. 60-35.4)

Our invention relates to jet propulsion and more particularly topropellants which are useful in connection therewith.

This is a division of my copending application Serial No. 486,236, filedMay 8, 1943, now U. S. Patent 2,573,471.

While our invention is capable of use in connection with the propulsionof a wide variety of different devices and vehicles, since it findsparticular utility in the propulsion of aircraft, its advantages aredescribed with relation to such use, it being understood that ourinvention is, however, not limited to such use.

Prior to our invention special means were always required to ignite thepropellants. For example, when liquid oxygen is used as an oxidizer andgasoline is used as a fuel, some auxiliary ignition means must always beprovided to initiate combustion of the propellants. This isobjectionable because it requires either a spark plug or other ignitoror means for heating the walls of the combustion chamber above theignition point of the propellant mixture making this system complex anddependent upon the operation of such ignition system.

While spontaneous combustion is obtained with our preferred combinationsof propellants which is especially effective when operating inaccordance with our preferred method it will be understood that thepropellants we have discovered offer advantages even when operatingunder other conditions.

The present invention relates to fuels, and oxidizers and theircombination as propellants and their method of injection into a jetmotor. Among the objects of our invention are: to provide more efficientand eifective propellants for jet propulsion systems; to provide anoxidizing agent which is easily combustible with a suitable fuel andwhich has a large amount of oxygen available for burning a fuel; toprovide propellants, that is, fuels and oxidizers, which arespontaneously combustible; to provide a method for utilizing suchpropellants to give smooth combustion and to eliminate danger ofexplosion; to obviate the difficulties attendant upon the use ofliquified gases; to eliminate the need of an auxiliary ignition systemto ignite the propellants.

Oxidizers As a result of a thorough investigation of the variousoxidizing agents which may be used as propellants we prefer to employnitric acid. Since water tends to retard combustion of the acid with anyfuel, the nitric acid should be substantially free of water. Thus, whitefuming 'nitric acid, which normally contains less than about 2% of waterby weight, is to be preferred to weaker solutions of nitric acid.However, we have found that more dilute solutions of nitric acid may beutilized provided that nitrogen dioxide is dissolved in the nitric acid;which is a way of increasing the concentration of an otherwise moredilute solution. Preferably the nitric acid should contain at leastabout 5% N02 but preferably at least about 15 to 20% N02. Such asolution of nitrogen dioxide is known as red fuming nitric acid andalmost all red fuming nitric acid which is commercially available inthis country contains between about 5% and 20% nitrogen dioxide byweight and less than about 5% water by weight. Specifications for nitricacid, obtainable commercially as red fuming nitric acid, are as follows:

Chemical composition:

HNOs 90.5% by wt. min. Water 2.5% by wt. max. N02 7.25% by wt. max.6.50%

by wt. min. Physical properties:

Density 1.5 min.-l.55 max. 70

Melting point -50 F. max.

Color, etc Orange to dark redfumes vigorously when exposed to air.

Specifications for nitric acid, obtainable commercially as white fumingnitric acid, are as follows:

Melting point -45 F. Color, etc Straw yellow to water white; fumesvigorously when exposed to air.

The term white fuming nitric acid as used herein means a nitric acidcontaining a maximum of about 2% water by weight.

The term red fuming nitric acid as used herein means a nitric acidcontaining at least about 5% N02 and a maximum of about 5% water, byweight.

Nitric acid of all types containing at least 80% HNOs is useful as anoxidizer. We have also found that liquid nitrogen dioxide is a verysatisfactory oxidizer.

To eliminate the requirement for providing the jet motor with specialigniting means, we employ nitric acid, and preferably red fuming nitricacid, substantially free of water, as an oxidizer.

Fuels We have discovered a family of fuels which are spontaneouslycombustible with the oxidizing agents hereinabove mentioned and whichare satisfactory for et pro pulsion provided that the propellants aresupplied to the combustion chamber under suitable operating conditions.These operating conditions are discussed more in detail hereinbelow.

We have found that the four groups of compounds listed below may beutilized as fuels. These groups are listed in the order of theireffectiveness.

Group I.Liquid organic compounds containing at least one amine radical,such as,

A. Aniline, orthotoluidine, and methylamine.

B. Liquid hydrocarbons, containing large percentages of such aminesubstituted organic compounds.

Group II.Highly unsaturated hydrocarbons: L1qu1d hydrocarbons of theacetylene type and containing a large fraction of unsaturated (doubleand triple) carbon bonds, or both, for example, divinyl acetylene,d1propargyl, and propargyl alcohol.

Group III .Liquid substances containing the elements having theproperties of lithium (Li), beryllium (Be), boron (B), aluminum (Al),magnesium (Mg), phosphorus (P), potassium (K), and sodium (Na). With theexception of phosphorus all of the foregoing elements are particularlyuseful in fuels because they generate large amounts of heat duringcombustion, and phosphorus is particularly useful because it has a lowignition temperature.

A. Liquid hydrides of those elements.

B. Liquid organo-metallic compounds containing one or more of suchelements.

0 Liquid fuels containing one or more such elements.

D. Liquid fuels containing one or more such elements in suspension.

3 fGroup I V.-Organic compounds having the properties Pyrole PyridinePinene Terpene Pinole Terpinola Hydrazine Ozonides Carbon disulphidecontaining phosphorus.

sow w Method of operation The above mentioned oxidizers and fuels may beused together'as' pairs of spontaneously combustible propellants atatmospheric temperature and pressure. However, if desired theseoxidizers and fuels" may be used with other fuels (such as gasoline) orother oxidizers (such as liquid oxygen respectively.

So far as we know we are the first to achieve spontaneous combustion injet propulsion systems at the temperature and pressure of the mediumsurrounding the jet motor and while other fuels and oxidizers might beutilized to accomplish such spontaneous combustion we prefer to use thefuels and oxidizers hereinbefore mentioned.

Certain difliculties are encountered when utilizing these propellantsfor propulsion Unless the propellants are. supplied to the. jet motorunder the proper conditions the motor is liable to fail completely,topulsate in its operation, or to explode, even though the propellantsare supplied at uniform rates.

These difliculties may be eliminated and certainly smoothness ofoperation secured by so relating the rates of injection of fuel andoxidizer to the size of the jet chamber and the inherent ignitionproperties of the mixture that explosion of the combustible mixture isavoided during the initial combustion, and subsequent injection occursat rates conducive to the combustion of the continuously suppliedpropellants so as to avoid the accumulation in the jet chamber of anysubstantial amount of the unburned propellants. To achieve this result,we initially inject propellants into the combustion chamber at ratessuch that the amount of propellants injected prior to the initiation ofcombustion is. less than about 20% of the volume of the combustionchamber.

After combustion has been initiated, the propellants may be injected ata greater rate than they are injected initially inasmuch as the timeinterval between their inection and combustion is reduced because of thehigher temperature and pressure of the mixture resulting from priorcombustion and the heating of the walls of the combustion chamber by theproducts of combustion.

In the drawing the figure shows a jet motor system including tanks andconduits for supplying propellants to the motor.

The fuels and oxidizers hereinbefore described are advantageouslyemployed in the propulsion of an aircraft by providing the fuel andoxidizer in separate containers 1'1 and 12 respectively connected in anysuitable manner as by pipes 13 and 14 to a jet or combustion chamber.Throttle valves 16 and 17 energized by electrical circuits 18' and 19are provided in said pipes to control the rates of supply of the fueland oxidizer respectively to the combustion chamber 15. A receptacle 20is connected by a conduit 21 having a pressure regulator 22 therein tothe receptacles 11 and 12 and is provided with a gas under pressure,preferably a gas inert with respect to either propellant. Preferably thecontainer for the fuel and the container for the oxidizer are connectedto a source of pressure adapted to force the contents of such containersinto the jet or combustion chamber at controlled rates determined by thedegree of opening of the valves in said ipes.

P The practice. of the method of our invention contemplates so relatingthe rates of injection of the oxidizer and of the fuel to the combustionor jet chamber to their inherent combustion properties and the size andtemperature of the chamber that smooth non-explosive combustion occursinitially and throughout the entire operation while providing thedesired quantity of propulsive power. Our invention is particularlyadvantageous when the combustion chamber is initially at atmospherictemperature, or at the temperature of any other medium in which themotor is to operate, as weare able to achieve combustion initiallywithout auxiliary ignition or preheating of the chamber or thepropellants.

If. the propellants are supplied atsuch. initial rates, then, when the.propellants are initially injected into the jet motor, the initiallyburned propellants soon till the combustion chamber with hightemperature gases and vapors which heat the incoming propellants therebyvaporizing them and reducing the ignition time lag. Then thesubsequently injected propellant-sburnspontaneously without anysubstantial accumulation of propellants in the liquid phase.

As an example, applied-1 to a combustion chamber having. a length ofaboutv 10': inches. and a cross sectional area of about 7 square inches,highly concentrated nitric acid and aniline. operate very satisfactorilywhen they are injected intothe combustion chamber initially and prior tocombustion at the rates of 3.6 lbs. per second and 2.4 lbs. per secondrespectively.

While these propellants and method of use and the apparatus for theiruse in propelling aircraft or other de vices,. which are hereinbeforedescribed, are fully capable. of providing. the advantages primarilystated, it will be. recognized by those skilled in the. art that variousIllOdlfi cations and alterations may be made therein while still.providing such advantages, and our invention is therefore to beunderstood as not limited tothe specific embodiments hereinbeforedescribed but as including all m0difi-- cations and variations thereofcoming within the scope of the claims which follow- We claim as ourinvention:

1. The method of developing thrust which comprises ejecting from areaction chamber the gaseous products; produced by the spontaneouscombustion of a compound selected from the group consisting of hydrazineand carbon disulphide containing. phosphorus, and acid selected from thegroup consisting of red fuming nitric acid and white fuming nitric acid.

2. The method of developing thrust which comprisesejecting from areaction chamber the gaseous products produced by the spontaneouscombustion of hydrazine.

and acid from: the group consisting, of red fuming nitric acid and whitefuming nitric: acid.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,573,471 Malina et a1. Oct. 30, 1951 FOREIGN PATENTS NumberCountry Date 405,645 Great Britain Jan. 29, 1934 576,227 Great BritainDec.. 3, 1937 OTHER. REFERENCES Mellor: A Comprehensive Treatise onInorganic and Theoretical Chemistry, vol. VIII, page 313. Pub. 1928 byLongrnans, Green & Co., New York and London. Copy in Division 59.

1. THE METHOD OF DEVELOPING THRUST WHICH COMPRISES EJECTING FROM AREACTION CHAMBER THE GASEOUS PRODUCTS PRODUCED BY THE SPONTANEOUSCOMBUSTION OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF HYDRAZINEAND CARBON DISULPHIDE CONTAINING PHOSPHORUS, AND ACID SELECTED